[Exim] redirect_router option

Hi!!....

    In a redirect router, I want to redirect to another router if a header
exist... I'm trying:

redirect_router = ${if eq {$h_X-Woo-Link:} {} {outfilter_router}
{outlink_router}}

but redirect_router is a string, not a expanded string (from the
documentation)... any ideas ?? it's posible to add this feature to the next
release ??

thankx in advance...

justo